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friction is now applied in a way similar to what the rigid body solver does

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This commit is contained in:
jingyuc 2021-09-08 19:00:55 -04:00
parent eef3b73cd2
commit ce765a8a88
3 changed files with 51 additions and 46 deletions
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9
examples/ReducedDeformableDemo/FreeFall.cpp
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@ -77,10 +77,11 @@ public:
// btRigidBody* rb0 = createRigidBody(mass, startTransform, shape);
// rb0->setLinearVelocity(btVector3(0, 0, 0));
startTransform.setOrigin(btVector3(0,4,0));
startTransform.setOrigin(btVector3(0,4,-1));
// startTransform.setRotation(btQuaternion(btVector3(1, 0, 1), SIMD_PI / 4.0));
btRigidBody* rb1 = createRigidBody(mass, startTransform, shape);
rb1->setLinearVelocity(btVector3(0, 0, 0));
rb1->setActivationState(DISABLE_DEACTIVATION);
rb1->setLinearVelocity(btVector3(0, 0, 4));
}
void stepSimulation(float deltaTime)
@ -273,10 +274,10 @@ void FreeFall::initPhysics()
getDeformableDynamicsWorld()->setLineSearch(false);
getDeformableDynamicsWorld()->setUseProjection(true);
getDeformableDynamicsWorld()->getSolverInfo().m_deformable_erp = 0.3;
getDeformableDynamicsWorld()->getSolverInfo().m_friction = 0.0;
getDeformableDynamicsWorld()->getSolverInfo().m_friction = 0.3;
getDeformableDynamicsWorld()->getSolverInfo().m_deformable_maxErrorReduction = btScalar(200);
getDeformableDynamicsWorld()->getSolverInfo().m_leastSquaresResidualThreshold = 1e-3;
getDeformableDynamicsWorld()->getSolverInfo().m_splitImpulse = true;
getDeformableDynamicsWorld()->getSolverInfo().m_splitImpulse = false;
getDeformableDynamicsWorld()->getSolverInfo().m_numIterations = 100;
// add a few rigid bodies
Ctor_RbUpStack();

86
src/BulletSoftBody/BulletReducedSoftBody/btReducedDeformableContactConstraint.cpp
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@ -51,6 +51,7 @@ btReducedDeformableRigidContactConstraint::btReducedDeformableRigidContactConstr
m_appliedNormalImpulse = 0;
m_appliedTangentImpulse = 0;
m_rhs = 0;
m_rhs_tangent = 0;
m_cfm = 0;
m_erp = infoGlobal.m_deformable_erp;
m_friction = infoGlobal.m_friction;
@ -115,6 +116,7 @@ btScalar btReducedDeformableRigidContactConstraint::solveConstraint(const btCont
// if (!m_collideStatic)
// {
std::cout << "deltaV_rel: " << deltaV_rel[0] << '\t' << deltaV_rel[1] << '\t' << deltaV_rel[2] << "\n";
std::cout << "deltaV_rel_normal: " << deltaV_rel_normal << "\n";
std::cout << "normal_A: " << m_contactNormalA[0] << '\t' << m_contactNormalA[1] << '\t' << m_contactNormalA[2] << '\n';
// }
@ -143,11 +145,11 @@ btScalar btReducedDeformableRigidContactConstraint::solveConstraint(const btCont
}
}
if (!m_collideStatic)
{
// if (!m_collideStatic)
// {
std::cout << "m_appliedNormalImpulse: " << m_appliedNormalImpulse << '\n';
std::cout << "deltaImpulse: " << deltaImpulse << '\n';
}
// }
// residual is the nodal normal velocity change in current iteration
btScalar residualSquare = deltaImpulse * m_normalImpulseFactor; // get residual
@ -157,31 +159,10 @@ btScalar btReducedDeformableRigidContactConstraint::solveConstraint(const btCont
// apply Coulomb friction (based on delta velocity, |dv_t| = |dv_n * friction|)
btScalar deltaImpulse_tangent = 0;
{
// trial velocity change
// deltaImpulse_tangent = m_friction * deltaImpulse;
// btScalar deltaV_tangent_trial = deltaImpulse_tangent * m_tangentImpulseFactor;
btScalar total_deltaV_rel_normal = m_appliedNormalImpulse * m_normalImpulseFactor;
btScalar deltaV_tangent_trial = abs(m_friction * total_deltaV_rel_normal);
// initial relative tangential veloity magnitude
btScalar v_rel_tangent = abs((Va - getVb()).dot(m_contactTangent));
std::cout << "v_rel_tangent: " << v_rel_tangent << '\n';
btScalar deltaV_rel_tangent = deltaV_rel.dot(m_contactTangent);
std::cout << "deltaV_rel_tangent: " << deltaV_rel_tangent << "\n";
btScalar v_rel_tangent_budget = v_rel_tangent - deltaV_rel_tangent;
// if the trial velocity change is greater than the current tangential relative velocity
if (deltaV_tangent_trial > v_rel_tangent_budget)
{
std::cout << "clamped!!\n";
deltaImpulse_tangent = v_rel_tangent_budget / m_tangentImpulseFactor;
}
else
{
std::cout << "ok. not too big\n";
deltaImpulse_tangent = deltaV_tangent_trial / m_tangentImpulseFactor;
}
// calculate how much impulse is needed
btScalar deltaV_rel_tangent = btDot(deltaV_rel, m_contactTangent);
btScalar impulse_changed = deltaV_rel_tangent * m_tangentImpulseFactorInv;
deltaImpulse_tangent = m_rhs_tangent - impulse_changed;
btScalar sum = m_appliedTangentImpulse + deltaImpulse_tangent;
btScalar lower_limit = - m_appliedNormalImpulse * m_friction;
@ -202,6 +183,7 @@ btScalar btReducedDeformableRigidContactConstraint::solveConstraint(const btCont
}
std::cout << "m_contactTangent: " << m_contactTangent[0] << "\t" << m_contactTangent[1] << "\t" << m_contactTangent[2] << "\n";
std::cout << "deltaV_rel_tangent: " << deltaV_rel_tangent << '\n';
std::cout << "deltaImpulseTangent: " << deltaImpulse_tangent << '\n';
std::cout << "m_appliedTangentImpulse: " << m_appliedTangentImpulse << '\n';
}
@ -315,25 +297,45 @@ void btReducedDeformableNodeRigidContactConstraint::warmStarting()
// we define the (+) direction of errors to be the outward surface normal of the rigid object
btVector3 v_rel = vb - va;
// get tangent direction of the relative velocity
m_contactTangent = (v_rel - v_rel.dot(m_contactNormalA) * m_contactNormalA).safeNormalize();
// tangent impulse factor
m_tangentImpulseFactor = (m_impulseFactor * m_contactTangent).dot(m_contactTangent);
btScalar velocity_error = btDot(v_rel, m_contactNormalA); // magnitude of relative velocity
btScalar position_error = 0;
if (m_penetration > 0)
btVector3 v_tangent = v_rel - v_rel.dot(m_contactNormalA) * m_contactNormalA;
if (v_tangent.norm() < SIMD_EPSILON)
{
// velocity_error += m_penetration / m_dt; // TODO: why?
m_contactTangent = btVector3(0, 0, 0);
// tangent impulse factor
m_tangentImpulseFactor = 0;
m_tangentImpulseFactorInv = 0;
}
else
{
// add penetration correction vel
position_error = m_penetration * m_erp / m_dt;
m_contactTangent = v_tangent.normalize();
// tangent impulse factor
m_tangentImpulseFactor = (m_impulseFactor * m_contactTangent).dot(m_contactTangent);
m_tangentImpulseFactorInv = btScalar(1) / m_tangentImpulseFactor;
}
// initial guess for normal impulse
{
btScalar velocity_error = btDot(v_rel, m_contactNormalA); // magnitude of relative velocity
btScalar position_error = 0;
if (m_penetration > 0)
{
// velocity_error += m_penetration / m_dt; // TODO: why?
}
else
{
// add penetration correction vel
position_error = m_penetration * m_erp / m_dt;
}
// get the initial estimate of impulse magnitude to be applied
m_rhs = -(velocity_error + position_error) / m_normalImpulseFactor;
}
// initial guess for tangential impulse
{
btScalar velocity_error = btDot(v_rel, m_contactTangent);
m_rhs_tangent = velocity_error * m_tangentImpulseFactorInv;
}
// get the initial estimate of impulse magnitude to be applied
// m_rhs = -velocity_error * m_normalImpulseFactorInv;
m_rhs = -(velocity_error + position_error) / m_normalImpulseFactor;
// warm starting
// applyImpulse(m_rhs * m_contactNormalA);

2
src/BulletSoftBody/BulletReducedSoftBody/btReducedDeformableContactConstraint.h
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@ -41,7 +41,9 @@ class btReducedDeformableRigidContactConstraint : public btDeformableRigidContac
btScalar m_appliedTangentImpulse;
btScalar m_normalImpulseFactor;
btScalar m_tangentImpulseFactor;
btScalar m_tangentImpulseFactorInv;
btScalar m_rhs;
btScalar m_rhs_tangent;
btScalar m_cfm;
btScalar m_erp;